1. Technical Field
This invention relates generally to water treatment, and more particularly to a system and related methodology for treating wastewater and the like with ozone and ultraviolet light for purification and disinfection purposes.
2. Background Information.
Recall that some water treatment systems bleach or oxidize an effluent such as wastewater using ozone and ultraviolet (UV) light. They do so in the process of purifying and disinfecting the water. Ozone in the water acts directly to kill bacteria and viruses and to oxidize undesirable compounds in the water. UV light also acts directly to kill bacteria and viruses. In addition, it serves as a catalyst for the disinfecting and oxidizing action of the ozone. So some water treatment systems combine both ozone and UV light processing.
However, sufficient UV light absorbency is necessary to maximize ozone reactivity and enhance chemical breakdown within the effluent stream. It is difficult to achieve with large flow rates. In addition, the complexity, expense, and potential hazards of adapting existing techniques to a system capable of processing large volumes of water can be prohibitive.
U.S. Pat. No. 4,865,749 suggests passing ozone bubbles through the water and running the ozonated water past an ultraviolet lamp. One problem with that technique is that only limited water surface area is contacted by the ozone bubbles. But another problem is that of insufficient UV light absorbency. Water volume, color, and turbidity impede UV light absorbency, and running the ozonated water past an ultraviolet lamp as suggested results in too much water volume, color and turbidity for effective UV light absorbency.
U.S. Pat. No. 4,273,660 uses a nozzle to inject the water into a UV chamber in an attempt to improve absorbency. The water swirls in a spiral path around a centrally located UV lamp. But water volume and flow rate still impede the process. U.S. Pat. No. 4,230,571 also spirals water around a UV lamp with the same drawback.
The residence time of the water to be treated in the UV chamber is a measure of the effectiveness of the process. Long residence times, up to 45 minutes, are required in some existing systems to achieve adequate water purification and disinfection. An improved system and methodology for ozone and UV light processing is needed with a reduced residence time. For a given throughput, reduced residence time results in a smaller treatment system, with associated lower capital and operating costs.